I'm going through the same thing, my son had packed lunch first week of school and I then tried him with dinners. The teacher told me that all he did was push the food around. He then asked me for packed lunch and said he just wanted mammy's food!
I think it might be a little bit of seperation anxiety on my son's part even though he has settled in really well in class. It's as if he wants a bit of home with him! I gave into him this week, but i'm trying to ease him into having dinners again, it's so much easier!
I agree though, they should try backing off and leaving him come round to the idea himself. the teacher should listen to you, you do know best!